LaserWriter 16/600 PS: TCP/IP Accounting (11/94)


Communication with PostScript printers for UNIX systems is done using the TranScript package from Adobe Systems. The TranScript driver carries on a conversation with the printer that includes status queries for deadlock and failure detection, as well as accounting.

PostScript interpreters nominally keep a counter of how many 'print this page' operators have been executed. These operators generally cause a piece of paper to be cycled through the printer engine. This counter may be the same as or independent of any page counters held by the print engine.

This counter can be queried by the PostScript code

statusdict begin pagecount == end

The host driver queries the page counter before and after the job and records the difference as the number of pages that job printed. In order to query this counter a bidirectional communication link is needed.

The preferred method to connect a printer to the RJO system is through a TCP/IP bidirectional link. This allows data transfers at network speeds, letting TCP perform flow control.

Some printers (or adapters) support TCP/IP, but only implement the LPD protocol. Print jobs are sent to the printer as if it was another UNIX computer running an lpd server. This approach is not viable unless logging and accounting information can be obtained from the printer via TCP/IP. This accounting information must include the user and host identifiers from the lpd control file.

You are correct that this isn't possible, the IP connection doesn't support bidirectional PostScript communication. The LaserWriter 16/600 PS can accept print jobs through TCP/IP, but this particular mechanism is batch oriented, with no provisions for obtaining accounting information from the printer.

Bidirectional communications is supported on the LocalTalk, EtherTalk, and the Parallel communication channels.


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Published Date: Feb 19, 2012